The last years have seen a rapid rise in the number of web sites that support a
"dark mode". Some pages offer an explicit light/dark switch. But typically the
selection is based on the browsers "prefers-color-scheme" CSS selector. It is
surprisingly difficult to change this browser default without switching the whole
operating system.

Follow the instructions below to switch to dark mode.

The color scheme preference of your browser is not setlightdark.

Chrome

For Chrome, the instructions depend on the system it is running on.

On Android

In Chrome, open the top-right "..." menu and go to "Settings"

Open "Themes"

Select "Dark"

On iOS

There is no direct way to enable dark mode only for Chrome on iOS. You have
to change the whole device to iOS via "Settings" → "Display &
Brightness".

On Windows

Chrome switches into dark mode when it is started with the --force-dark-mode command line flag.

Close all Chrome instances

Shift-Right click the Chrome shortcut in the taskbar or on the desktop

Select "Properties"

In the "Shortcut" tab, append --force-dark-mode to the "Target" field

Close the dialog with "OK"

Restart Chrome with that shortcut

Safari

Safari doesn't have a separate setting for dark mode. It always follows the operating system setting.

Changing the system setting on iOS

Open Settings

Open "Display & Brightness"

Select "Dark"

Changing the system setting on MacOS

Open the system settings in the Apple menu

Open the "General" dialog

Select the "Dark" appearance

Firefox

Firefox has hidden configuration option that enables dark mode:

Type about:config into the address bar and press Enter

Type ui.systemUsesDarkTheme into the search bar

The search will not find anything, but allow you to add a new preference with that name

Set the property type to "Number" and click the "+" button to create:

Enter the value "1" to enable dark mode and click the check mark to save: